1. Field
A scroll compressor is disclosed herein.
2. Background
Generally, a scroll compressor is being widely used in air conditioners, for example, in order to compress a refrigerant, owing to its advantages that a compression ratio is relatively higher than that of other types of compressors, and a stable torque is obtainable as processes for suction, compressing, and discharging a refrigerant are smoothly performed. A behavior characteristic of the scroll compressor is determined by a non-orbiting wrap (hereinafter, referred to as a “fixed wrap”) of a non-orbiting scroll (hereinafter, referred to as a “fixed scroll”) and an orbiting wrap of an orbiting scroll. The fixed wrap and the orbiting wrap may have any shape, but they generally have a shape of an involute curve for easy processing. The involute curve means a curved line corresponding to a moving path drawn by the end of a thread when the thread wound around a basic circle having any radius is unwound. In a case of using such an involute curve, the fixed wrap and the orbiting wrap stably perform a relative motion since they have a constant thickness, thereby forming a compression chamber to compress a refrigerant.
As a volume of the compression chamber of the scroll compressor is decreased towards an inner side from an outer side, a suction chamber is formed at the outer side and a discharge chamber is formed at the inner side. A refrigerant suctioned into the suction chamber has a temperature of about 18° C., and a refrigerant discharged from the discharge chamber has a temperature of about 80° C. However, the orbiting scroll is not greatly influenced by a refrigerant discharge temperature, as a rear surface thereof is positioned between the orbiting scroll and the fixed scroll in a supported state by a main frame. On the other hand, the fixed scroll is exposed to a refrigerant discharge temperature as a plate portion or plate, which forms a rear surface thereof is coupled to an inner space of a casing or a discharge cover or a high and low pressure separation plate.
As the rear surface of the fixed scroll is exposed to a refrigerant discharge temperature, the plate portion of the fixed scroll is entirely influenced by the refrigerant discharge temperature to be thermally-expanded. On the other hand a fixed wrap, provided on one side surface of the plate portion of the fixed scroll and forming the compression chamber, is not entirely influenced by a refrigerant discharge temperature. More specifically, a part or portion of the fixed wrap near a suction chamber is influenced by a suction temperature, a part or portion of the fixed wrap near an intermediate pressure chamber is influenced by an intermediate compression temperature, and a part or portion of the fixed wrap near a discharge chamber is influenced by a discharge temperature. That is, the fixed wrap has a different thermal expansion rate according to a region. As the plate portion of the fixed scroll is more thermally-transformed than the fixed wrap, the fixed wrap is transformed in a contracted shape.
Especially, as the fixed wrap near the suction chamber directly contacts a cold suction refrigerant having a temperature of about 18° C., the fixed wrap near the suction chamber is more transformed than other regions, because it has a tendency to be contracted towards a central region. This may cause an orbiting wrap contacting the fixed wrap formed near the suction chamber, to be pushed by the bent fixed wrap. As a result, the orbiting wrap having a crank angle of 180° at an opposite side is paced from the fixed wrap, resulting in a compression loss.
Further, as a specific region of the fixed wrap is more thermally-transformed than other regions, the fixed wrap and the orbiting wrap may excessively contact each other. This may increase a frictional loss or abrasion between the fixed scroll and the orbiting scroll.